Clearly this song is about the paparazzi and the hell they made (and still make) her life. "all the flashing trying to cash in hurts my eyes" sums it up pretty well, if you've seen how they crowd her and shove their cameras in her face, you'll see why she got to the stage she did (and why she wears sunglasses indoors etc). The line "they all want to see what you're made of" also illustrates the vicious nature of the tabloid industry and how they push people over the edge and then wonder why it happened.
One of the best songs I've heard from Britney.